#include <iomanip>
#include <iostream>
using namespace std;

int main()
{
	double w = 0.0;
	double s = 0.0;
	cin >> w;
	if (w <= 1)
	{
		s = 1;
	}
	else
	{
		int t = w;
		if (t == w)
		{
			s = 1 + (t - 1) * 0.8;
		}
		else
		{
			s = 1 + t * 0.8;
		}
	}
	cout << fixed << setprecision(2) << s;
	return 0;
}
